1. Field of the Invention
The present invention relates to a display device and a method for transferring image data.
2. Description of the Related Art
Well-known as a display device mentioned above is, e.g., what is shown in FIG. 3 (Patent Document 1). As shown in the FIG. 3 the display device 1 includes a CPU 4 controlling the whole display device 1 as a first controller, a ROM 5 in which an image data is stored as a first memory, a graphic display controller 6 (hereafter referred to as a GDC) controlling a driver 3 and displaying the image data on a liquid crystal display 2, a VRAM 7 temporally storing the image data displayed on the liquid crystal display 2 as a second memory, and a data bus 8 mutually connecting the CPU 4, the ROM 5 and the GDC 6.
The display device 1 is required to temporally transfer and store the image data stored in the ROM 5 to the VRAM 7 in order to display the image data stored in the ROM 5 on the liquid crystal display 2.
As a conventional method for transferring, steps shown in FIG. 4 are performed. FIGS. 4 (A) to (E) each show a time chart of a read signal of the display device 1 shown in FIG. 3, a state of the ROM 5, a write signal, a state of the GDC 6, and the image data on the bus 8. First, the CPU 4 outputs a read signal to the ROM 5 (FIG. 4 (A)). The ROM 5, corresponding to output of the read signal, outputs the image data onto the data bus 8 (FIG. 4 (B), (E)). The CPU 4 reads the image data outputted on the data bus 8 and stores the image data into the internal memory not shown.
Completing reading, the CPU 4 outputs a write signal to the GDC 6 (FIG. 4 (C)) while outputting the image data onto the data bus 8 (FIG. 4 (E)). The GDC 6, corresponding to the write signal, reads the image data outputted on the data bus 8 and writes the image data into the VRAM 7 (FIG. 4 (D), (E)).
However, in the method above mentioned, the CPU 4 has been required to read the image data stored in the ROM 5 before writing the image data from the CPU 4 via the GDC 6 into the VRAM 7. Namely, there has been a problem in which the conventional method for transferring mentioned above has been required to perform two steps of reading and writing, causing much time for transferring.
[Patent Document 1] JP, A, 2007-248965
An object of the present invention is to provide a display device and a method for transferring image data achieving shortening process time required to transfer image data without greater processing capacity.